The research program developed in the proposal aims to understand how auditory cognition, in general, and speech perception, in particular, is mediated by cortical structures. Two broad questions are addressed. First, what is the functional neuroanatomy of speech sound processing? Second, are there cortical time-based mechanisms that provide a logistical basis for the analysis of auditory signals? These two questions are addressed in a series of magnetoencephalography (MEG) studies. Both research goals build on recent findings, primarily from neuroscience and cognitive neuroscience that suggest a new perspective on the functional anatomy and physiology of speech sound processing. Results from hemodynamic imaging studies (PET, fMRI) as well as electromagnetic recording techniques (EEG, MEG) show that the functional neuroanatomy of speech perception (i) is more bilaterally organized than previously assumed and (ii) that auditory areas in the temporal lobe play a core role, but that parietal and frontal areas are critically implicated in specific aspects of speech sound processing as well. Furthermore, neurophysiological results, both at the single-unit and systems levels, point to the importance of timing mechanisms in the representation and processing of auditory signals. Because MEG is a non-invasive recording technique that has the necessary temporal resolution (ms) to study neurophysiological timing phenomena and can also localize the activity in a useful anatomic context, it is the appropriate tool to address both broader questions.